Fix GitLab API pagination

[gavinelder]

Summary

• expose checked HTTP responses to repository providers so pagination headers are available
• follow GitLab-provided rel="next" links for branch and tag listings
• request GitLab’s maximum page size and reject unsafe or cyclic continuation links

Test plan

• ./gradlew :nextflow:test --tests nextflow.scm.RepositoryProviderTest --tests nextflow.scm.GitlabRepositoryProviderTest --rerun-tasks

Implementation note

The GitLab override does not retain the base helper’s @Memoized inner call. In practice, branch and tag listings are called once per provider instance, and memoizing a method whose key includes a Closure argument provides little useful reuse. Keeping pagination state local also avoids caching response-header traversal.

Stack

• Base: ADR: GitLab repository tree pagination #7401
• This PR contains the reusable pagination layer; repository-tree pagination follows in Fix GitLab repository tree pagination #7403.